1. Field of the Invention
The present invention relates to rotary anode devices for generating a beam of X-rays.
2. Description of the Prior Art
There is already known, as described in the document EP-0 170 551, for example, a radiological device including a rotary anode radiogenic tube. The radiogenic tube comprises a vacuum enclosure, delimited by a sealed wall, and in which is disposed a cathode adapted to generate a flux of electrons. In the vacuum enclosure there is also a rotary anode, driven in rotation about a rotation axis by a rotor with magnetic bearings. The rotary anode receives at its periphery the flux of electrons coming from the cathode and thus emits X-rays that are directed toward an exit. The magnetic bearings are controlled to move the rotor along its rotation axis and thus to move the rotary anode, in response to a sensor of the position of the beam of X-rays at the exit, to maintain fixed the position of the beam of X-rays at the exit. This eliminates the deleterious influence of unintentional movements of the rotary anode that may result in particular from thermal expansion or from deformation of certain elements of the device.
The rotary anode X-ray emitter devices known at present are relatively bulky because, in addition to the rotary anode and its device for driving rotation in a vacuum enclosure, they necessitate an external vacuum pump to generate and to maintain the vacuum in the vacuum enclosure.
Furthermore, the known means for driving the rotary anodes in rotation generate vibrations that limit the possibilities of use in certain applications such as electronic microscopy, monitoring the crystallization of polymers, measuring small structures or multilayers in the fabrication of semiconductors.
Furthermore, the rotary anode X-ray generators used at present are costly, and require a great deal of maintenance. Also, the brightness of the source is insufficient, and there is a benefit in increasing that brightness to improve the focusing of the radiation onto small samples.